This invention relates generally to chairs, and in particular to the structure of the chair back. In the past, chair backs have been manufactured which use a pair of structural shells. An inner structural shell is typically used which provides the foundation for the chair back, and provides the structure to which the upholstery is attached. An outer structural shell can optionally be attached to the back of the inner structural shell to conceal the attachment of the upholstery to the inner structural shell. In the past, the inner and outer structural shells have been typically made of plywood. In order to satisfy the customer's desire for a variety of models to choose from, manufacturers have been forced to produce a variety of different chair back models. When the chair backs have utilized inner and outer structural shells, producing a variety of models has required production of both different sets of outer structural shells and different sets of inner structural shells. Production of these different structural shells increases the cost and complexity of manufacturing the chairs.
Prior chair backs have typically had a three-dimensionally curved front surface to provide more comfort to the user of the chair. In the past, in order to create a chair back having a three-dimensionally curved front surface, either the entire plywood shell (front and back) had to be molded into a three-dimensional shape, or molded cushioning or foam had to be attached to the plywood. Molded cushioning or foam, however, is more expensive than unmolded slab ) foam or cushioning. Molding plywood into a three-dimensionally curved shape is also not only expensive, but technically difficult. Ensuring that the curvature of the plywood is acceptably consistent from one chair back to the next is difficult. The storage of three-dimensionally curved plywood shells is also difficult because stacking the shells tends to bend the plywood out of its desired shape. Further, in the past, to use an outer shell with a three-dimensionally curved inner shell has required that the outer shell also be three-dimensionally curved. Molding a plywood outer shell to also be three-dimensionally curved adds further difficulty to making the chair.
The desirability of a chair back having a structure which can simply and inexpensively be altered to produce a variety of chair back models can therefore be seen. The desirability of a chair back having a three-dimensionally curved front surface which does not use expensive molded foam and which overcomes the above difficulties can also be seen.